I'm not sure this is really an argument, but if we can remember what happened yesterday, isn't this to some extent time travel?

By this same logic we could define slope as the change in x over y or s = dx/dy. Does this definition make it impossible to move along the y axis because then the slope of our movement would be dy/dy? No. but it does say that if you move along the y axis your slope will be a constant.

The parent argument's error is that the math in physics represents a homomorphism between an abstract a priori construct we call math and a physical nature. Without properly understanding the underlying form of nature, the homomorphism breaks down. The last I checked, no one knows what time is, or how matter really behaves with respect to it. Therefore, dt/dt=1 does not rule out the possibility for time travel.